Delineation Of Gross Tumor Volume Research Articles

An Automated Multiparametric MRI Quantitative Imaging Prostate Habitat Risk Scoring System for Defining External Beam Radiation Therapy Boost Volumes

To develop a prostate tumor habitat risk scoring (HRS) system based on multiparametric magnetic resonance imaging (mpMRI) referenced to prostatectomy Gleason score (GS) for automatic delineation of gross tumor volumes. A workflow for integration of HRS into radiation therapy boost volume dose escalation was developed in the framework of a phase 2 randomized clinical trial (BLaStM). An automated quantitative mpMRI-based 10-point pixel-by-pixel method was optimized to prostatectomy GSs and volumes using referenced dynamic contrast-enhanced and apparent diffusion coefficient sequences. The HRS contours were migrated to the planning computed tomography scan for boost volume generation. There were 51 regions of interest in 12 patients who underwent radical prostatectomy (26 with GS ≥7 and 25 with GS 6). The resultant heat maps showed inter- and intratumoral heterogeneity. The HRS6 level was significantly associated with radical prostatectomy regions of interest (slope 1.09, r = 0.767; P < .0001). For predicting the likelihood of cancer, GS ≥7 and GS ≥8 HRS6 area under the curve was 0.718, 0.802, and 0.897, respectively. HRS was superior to the Prostate Imaging, Reporting and Diagnosis System 4/5 classification, wherein the area under the curve was 0.62, 0.64, and 0.617, respectively (difference with HR6, P < .0001). HRS maps were created for the first 37 assessable patients on the BLaStM trial. There were an average of 1.38 habitat boost volumes per patient at a total boost volume average of 3.6 cm3. An automated quantitative mpMRI-based method was developed to objectively guide dose escalation to high-risk habitat volumes based on prostatectomy GS.

Influence of MRI-CT fusion image on gross tumor volume delineation and dose distribution for radiation of primary tumors of cervical vertebra

Objective To compare the differences of gross tumor volume (GTV) and dose distribution between MRI-CT fusion imaging and CT-based imaging and investigate the dose difference in the therapeutic regime. Methods Ten patients diagnosed with primary tumors of the cervical vertebra between 2013 and 2014 were enrolled. Prior to radiotherapy, the imaging data of MRI examination (GE Discovery MR 750 3.0T) were collected, transfered into the Eclipse system and subject to fusion with CT images. GTV delineation, organ at risk (OAR) delineation and dose distribution discrepancy induced by target volume differences were analyzed and statistically compared between the MRI-CT fusion and CT-based images. GTV delineation and dose parameters among different radiologists between two approches were analyzed by analysis of variance (ANOVA) and paired t-test. Non-normally distributed variables were analyzed by Wilcoxon rank-sum test. The reliability of intraclass correlation coefficient (ICC) was assessed. Results The GTVMRI-CT volume was larger compared with the GTVCT volume. The volume overlap index was 0.84±0.17.The cordMRI-CT volume was significantly less than the cordCT volume (P=0.001). For 5 radiologists, the ICCMRI-CT was larger than ICCCT. The DmaxMRI-CT of the spinal cord was (46.00±1.09) Gy, significantly less than (52.39±1.34) Gy for the DmaxCT(P=0.014). Conclusions It is unlikely to miss the target delineation on MRI-CT fusion imaging. MRI-CT fusion imaging can minimize the discrepancy of interobserver radiologists and cause dosimetric advantages. Key words: Tomotherapy, X-ray computed; Magnetic resonance imaging; Gross tumor volume; Cervical neoplasm/intensity-modulated radiotherapy

Velocity-based Adaptive Registration and Fusion for Fractionated Stereotactic Radiosurgery Using the Small Animal Radiation Research Platform

To implement Velocity-based image fusion and adaptive deformable registration to enable treatment planning for preclinical murine models of fractionated stereotactic radiosurgery (fSRS) using the small animal radiation research platform (SARRP). C57BL6 mice underwent 3 unique cone beam computed tomography (CBCT) scans: 2 in the prone position and a third supine. A single T1-weighted post-contrast magnetic resonance imaging (MRI) series of a murine metastatic brain tumor model was selected for MRI-to-CBCT registration and gross tumor volume (GTV) identification. Two arms were compared: Arm 1, where we performed 3 individual MRI-to-CBCT fusions using rigid registration, contouring GTVs on each, and Arm 2, where the authors performed MRI-to-CBCT fusion and contoured GTV on the first CBCT followed by Velocity-based adaptive registration. The first CBCT and associated GTV were exported from MuriPlan (Xstrahl Life Sciences) into Velocity (Varian Medical Systems, Inc, Palo Alto, CA). In Arm 1, the second and third CBCTs were exported similarly along with associated GTVs (Arm 1), while in Arm 2, the first (prone) CBCT was fused separately to the second (prone) and third (supine) CBCTs, performing deformable registrations on initial CBCTs and applying resulting matrices to the contoured GTV. Resulting GTVs were compared between Arms 1 and2. Comparing GTV overlays using repeated MRI fusion and GTV delineation (Arm 1) versus those of Velocity-based CBCT and GTV adaptive fusion (Arm 2), mean deviations±standard deviation in the axial, sagittal, and coronal planes were 0.46±0.16, 0.46±0.22, and 0.37±0.22mm for prone-to-prone and 0.52±0.27, 0.52±0.36, and 0.68±0.31mm for prone-to-supine adaptive fusions, respectively. Velocity-based adaptive fusion of CBCTs and contoured volumes allows for efficient fSRS planning using a single MRI-to-CBCT fusion. This technique is immediately implementable on current SARRP systems, facilitating advanced preclinical treatment paradigms using existing clinical treatment planning software.

Impact of Magnetic Resonance Imaging on Gross Tumor Volume Delineation in Non-spine Bony Metastasis Treated With Stereotactic Body Radiation Therapy

This study investigates the inter-observer variability of contouring non-spine bone metastases using the planning CT alone vs. the addition of MRI T1 and T2 imaging sequences. 10 cases of non-spine bone metastases treated with SBRT at our institution were selected. The gross tumor volume (GTV) for each case was delineated by six SBRT radiation oncologists (RO) and one diagnostic radiologist (DR) on the treatment planning CT. After a minimum of three months, each case was re-contoured on the CT fused with a MRI T1 sequence followed by a MRI T2 sequence. STAPLE consensus contours were created from the RO volumes and inter-observer variability was measured using both κ agreement and the Dice coefficient (DSC). In total, 180 RO contours were analyzed within three datasets (CT, CT + MRI T1 and CT + MRI T1 + MRI T2). The mean GTV was 16.95 cm3 (range, 0.12-269.6 cm3). The RO κ agreement was 0.6129 based on CT alone, and significantly increased to 0.7045 in the CT + MRI T1 (P = .042) dataset and 0.7017 in the CT + MRI T1 + MRI T2 dataset (P = .048). The mean DSC in the CT alone dataset was 0.7047, and significantly increased to 0.7628 in the CT + MRI T1 dataset (P < .001) and 0.7544 in the CT + MRI T1 + MRI T2 dataset (P = .001). There were no statistical differences in RO κ agreement (P = .948) or mean DSC (P = .573) when comparing the CT + MRI T1 and CT + MRI T1 + MRI T2 datasets. The DSC agreement between DR and RO volumes was lowest (0.6887) in the CT alone dataset and significantly increased to 0.7398 in the CT + MRI T1 dataset (P = .003) and 0.7342 in the CT + MRI T1 + MRI T2 dataset (P = .008). The fusion of MRI T1 images to CT significantly reduced inter-observer variability amongst RO's in delineating non-spine bone metastases, and improved agreement between GTVs delineated by the RO to the DR.

Differential Dose Distribution in Transition from 3-D CRT to IMRT Treatment Plans for Glioblastoma Multiforme' at Stage III or IV: A Clinical Study of a Brain Tumor

&lt;p&gt;&lt;span&gt;Advancement in Cancer Therapy Technology (CTT) due to Software, Hardware and precise delivery of radiation dose has enhanced the quality of life of cancer patients. This report aims at the application of 3-D CRT (Three Dimensional Conformal Radiation Therapy) and IMRT (Intensity Modulated Radiation Therapy) for a quality of treatment. Other anatomical sites viz. Prostate, Lung, etc. may also be treated provided a better tool is applied for target delineation for which FUSION of CT and MRI images are used to ascertain differences in tissue density. This Fusion image of 3 mm slices offer accurate contouring of the tumor. The oncologist and/or physicist perform delineation of (I) GTV (Gross Tumor Volume), (II) CTV (Clinical Target Volume), (III) PTV (Planning Target Volume), (IV) TV (Treated Volume) and (V) OARs (Organs at Risk). This is done to secure conformal dose distribution and justify the clinical objectives of Tumor Control Probability (TCP) by reducing the normal tissue complication probability (NTCP). &lt;span&gt; &lt;/span&gt;&lt;span&gt; &lt;/span&gt;The implication of this study outlines the fundamental goal of effective treatment procedures by comparing treatment plans of 3-D CRT and IMRT. Tolerance levels of dose to different organs are optimized by the analysis of random and systemic geometrical deviations, margin on target volumes, conformity index (CI), patient selection process and, of course, the shape and stage of target. The comparative parameters of treatment plans are segmented and tabulated to implicate the application of necessary tools to decide on a treatment plan for similar patients.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Bangladesh J. Nuclear Med. 19(1): 64-67, January 2016&lt;/span&gt;&lt;/p&gt;

Appropriate magnetic resonance imaging techniques for gross tumor volume delineation in external beam radiation therapy of locally advanced cervical cancer.

BackgroundAccurate delineation of the gross tumor volumes (GTV) is a prerequisite for precise radiotherapy planning and delivery. Different MRI sequences have different advantages and limitations in their ability to discriminate primary cervical tumor from normal tissue. The purpose of this work is to determine appropriate MRI techniques for GTV delineation for external-beam radiation therapy of locally advanced cervical cancer (LACC).Materials and MethodsGTVs were delineated on the MRI, CT, and PET images acquired for 23 LACC patients in treatment positions to obtain GTVs on CT (GTV-CT), on various MRI sequences including T1 (GTV-T1), T2 (GTV-T2), T1 with fat suppression and contrast (GTV-T1F+), DWI-ADC (GTV-ADC) and on PET were generated using the threshold of 40% of maximum SUV (GTV-SUV40%) as well as SUV of 2.5 (GTV-SUV2.5). MRI, CT and PET were registered for comparison. The GTVs defined by MRI were compared using the overlap ratio (OR) and relative volume ratio (RVR). The union of GTV-T2 and GTV-ADC was generated to represent the MRI-based GTV (GTV-MRI).ResultsThe differences between GTV-T2 and other MRI GTVs are significant (P < 0.05). The average ORs for GTV-T1, GTV-T1F+, and GTV-ADC related to GTV-T2 were 86.3%, 81.6%, and 61.6% with the corresponding average RVRs 113.8%, 112.3% and 77.2%, respectively. There is no significant difference between GTV-T1 and GTV-T1F+. GTV-ADC was generally smaller than GTV-T2, however, encompassed suspicious regions that are uncovered in GTV-T2 (up to 16% of GTV-T2) because of different imaging mechanisms. There was significant difference between GTV-MRI, GTV-SUV2.5, GTV-SUV40%, and GTV-CT. On average, GTV-MRI is 18.4% smaller than GTV-CT.ConclusionsMRI provides improved visualization of disease over CT or PET for cervical cancer. The GTV from the union of GTV-T2 and GTV-ADC provides a reasonable GTV including tumor region defined anatomically and functionally with MRI and substantially reduces the conventional GTV defined on CT.

Improvement of CT Imaging with a Metal Artifact Reduction Technique for Radiation Treatment Planning-Fundamental Study of Structure Delineation and Dose Calculation

In radiotherapy planning, CT images are widely used to delineate the gross tumor volume (GTV) and the organs at risks (OARs), which allows for the calculation of the dose distribution to each structure. The delineated contours of the GTV and OARs may become inaccurate, and subsequently result in the inaccurate derivation of the dose distribution, if there are metal artifacts present in the CT image. The metal artifact reduction technique, single energy metal artifact reduction (SEMAR), installed on the CT system (Aquilion ONETM Vision Edition, Toshiba Medical Systems Corporation) could potentially reduce metal artifacts. Therefore, we investigated whether SEMAR can improve the accuracy of delineation, and subsequently the dosimetric accuracy, in the treatment planning process. Using an acrylonitrile-butadiene-styrene resin phantom (RT-3000-New, R-Tech. Inc, Tokyo, Japan), titanium bars were inserted on both the left and right sides, and four types of electron density inserts (rods) were separately inserted in the middle. The electron densities of the rods were 0.90, 0.96, 1.07, and 1.09. After CT images were acquired, SEMAR-ON (when applying the SEMAR correction) images were generated. On both SEMAR-ON and SEMAR-OFF (when not applying the SEMAR correction) images, the rod contours were delineated automatically, using a CT value threshold. This threshold was selected so that the area of the automatically delineated contour was 615.4 mm2. The difference in the contour area of SEMAR-ON, SEMAR-OFF, and no metal artifact images were compared using the dice coefficient. When SEMAR was used, the dice coefficient improved by 57.4%. Therefore, SEMAR was considered to be useful in improving the accuracy of GTV and OAR delineation.

Pancreatic gross tumor volume contouring on computed tomography (CT) compared with magnetic resonance imaging (MRI): Results of an international contouring conference

PurposeAccurate identification of the gross tumor volume (GTV) in pancreatic adenocarcinoma is challenging. We sought to understand differences in GTV delineation using pancreatic computed tomography (CT) compared with magnetic resonance imaging (MRI). Methods and materialsTwelve attending radiation oncologists were convened for an international contouring symposium. All participants had a clinical and research interest in pancreatic adenocarcinoma. CT and MRI scans from 3 pancreatic cases were used for contouring. CT and MRI GTVs were analyzed and compared. Interobserver variability was compared using Dice's similarity coefficient (DSC), Hausdorff distances, and Jaccard indices. Mann-Whitney tests were used to check for significant differences. Consensus contours on CT and MRI scans and constructed count maps were used to visualize the agreement. Agreement regarding the optimal method to determine GTV definition using MRI was reached. ResultsSix contour sets (3 from CT and 3 from MRI) were obtained and compared for each observer, totaling 72 contour sets. The mean volume of contours on CT was significantly larger at 57.48 mL compared with a mean of 45.76 mL on MRI, P = .011. The standard deviation obtained from the CT contours was significantly larger than the standard deviation from the MRI contours (P = .027). The mean DSC was 0.73 for the CT and 0.72 for the MRI (P = .889). The conformity index measurement was similar for CT and MRI (P = .58). Count maps were created to highlight differences in the contours from CT and MRI. ConclusionsUsing MRI as a primary image set to define a pancreatic adenocarcinoma GTV resulted in smaller contours compared with CT. No differences in DSC or the conformity index were seen between MRI and CT. A stepwise method is recommended as an approach to contour a pancreatic GTV using MRI.

Reproducibility of radiomic features with GrowCut and GraphCut semiautomatic tumor segmentation in hepatocellular carcinoma

Background: The reproducibility of radiomic features is a critical challenge facing radiomic models of tumor prediction or prognosis. The aim of this study is to evaluate the reproducibility of radiomic features with the GrowCut and GraphCut semi-automatic tumor segmentation methods in hepatocellular carcinoma (HCC) CT images. Methods: Computed tomography (CT) data sets (arterial enhanced phase) of 15 patients with HCC were randomly selected in this study. To acquire the gross tumor volume (GTV), semi-automatic segmentation with the GrowCut and GraphCut methods was implemented in 3D Slicer software by two independent observers. Meanwhile, manual delineation of the GTV was implemented by five abdomen radiation oncologists in this study. We divided the sample into three groups: the GrowCut group, the GraphCut group and manual group. Radiomic features (including tumor intensity histogram-based features, textural features and shape-based features) were extracted using the Imaging Biomarker Explorer (IBEX) software. The intraclass correlation coefficient (ICC) was applied to assess the reproducibility of all radiomic features. Results: The radiomic features in the GrowCut group (ICC =0.87±0.19) showed higher reproducibility compared with the radiomic features in the GraphCut group (ICC =0.82±0.24, P Conclusions: Our study reveals that variations exist in the reproducibility of quantitative imaging features extracted from tumor regions segmented using different methods. The 3D Slicer can serve as a better alternative to the manual delineation, and care must be taken when selecting segmentation tools to draw the tumor region.

Impact of pixel-based machine-learning techniques on automated frameworks for delineation of gross tumor volume regions for stereotactic body radiation therapy

The aim of this study was to investigate the impact of pixel-based machine learning (ML) techniques, i.e., fuzzy-c-means clustering method (FCM), and the artificial neural network (ANN) and support vector machine (SVM), on an automated framework for delineation of gross tumor volume (GTV) regions of lung cancer for stereotactic body radiation therapy. The morphological and metabolic features for GTV regions, which were determined based on the knowledge of radiation oncologists, were fed on a pixel-by-pixel basis into the respective FCM, ANN, and SVM ML techniques. Then, the ML techniques were incorporated into the automated delineation framework of GTVs followed by an optimum contour selection (OCS) method, which we proposed in a previous study. The three-ML-based frameworks were evaluated for 16 lung cancer cases (six solid, four ground glass opacity (GGO), six part-solid GGO) with the datasets of planning computed tomography (CT) and 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT images using the three-dimensional Dice similarity coefficient (DSC). DSC denotes the degree of region similarity between the GTVs contoured by radiation oncologists and those estimated using the automated framework. The FCM-based framework achieved the highest DSCs of 0.79±0.06, whereas DSCs of the ANN-based and SVM-based frameworks were 0.76±0.14 and 0.73±0.14, respectively. The FCM-based framework provided the highest segmentation accuracy and precision without a learning process (lowest calculation cost). Therefore, the FCM-based framework can be useful for delineation of tumor regions in practical treatment planning.

Pretreatment T2-Weighted Fluid Attenuated Inversion Recovery (T2-FLAIRpre) MRI May Improve Gross Tumor Volume Delineation for Recurrent Glioblastoma Treated with Salvage Hypofractionated Stereotactic Radiation Therapy

Few treatment options exist for recurrent GBM. HFSRT has been used as a salvage treatment strategy. Gross tumor volume (GTV) is usually based on pretreatment contrast enhanced T1-weighted (T1-contrastpre) MR image. T2-FLAIRpremay detect additional subtle signal of tumor infiltration. This study aimed to investigate the patterns of recurrence following salvage HFSRT using T2-FLAIR image in addition to T1-contrast in target delineation for HFSRT. We retrospectively examined 13 patients with recurrent GBM treated with HFSRT from 2015 to 2017 who had local recurrence following HFSRT. A median dose of 30 (25-35) Gy in 5 to 10 fractions was delivered. The median time between HFSRT and recurrence after HFSRT was 178 (48-259) days. Diagnostic MRI was performed before and 4 weeks after HFSRT, and then every 4 - 8 weeks. Separate GTVs using T1-contrastpre only, T2-FLAIRpre only, or T1pre+T2pre, were contoured blindly by a single radiation oncology physician. Recurrence volume was delineated on the post-treatment T1-contrast (T1-contrastpost) MRI at the time of progression. The volume overlapping between pretreatment GTV and recurrence volume was calculated. The centroid distance between pre- and post-treatment volumes was measured as well. Wilcoxon test was used to assess the statistical significance of differences. The median volumes overlapping between T1-contrastpre, T2-FLAIRpre, T1pre+T2pre and T1-contrastpost were 18% (range: 0-100%, Q1: 12%, Q3: 40%), 52% (range: 0-90%, Q1: 24%, Q3: 59%) and 53% (range: 0-100%, Q1: 26%, Q3: 77%), respectively. The recurrent volume overlapping with T1pre+T2pre was significantly larger than the overlap with T1-contrastpre (p=0.003). The median volume difference between T1-contrastpre and T2-FLAIRpre volumes resided in the recurrence volume was 3.9 cm3 (range: 0-11.5 cm3, Q1: 0.2 cm3, Q3 5.6 cm3). The centroid distance between volumes did not show significant difference. The median centroid distances between recurrence volume and T1-contrastpre volume, T2-FLAIRpre volume, and T1pre+T2prevolume were 1.3 cm (range: 0.3-4.9 cm, Q1: 0.8, Q3: 2.00), 1.3 cm (range: 0.3-4.7 cm, Q1: 0.8 cm, Q3: 2 cm) and 1.2 cm (range: 0.2-1.2 cm, Q1: 0.7 cm, Q3: 2.1 cm), respectively. A significant volume of recurrence occurred in the T1pre+T2pre region beyond the T1-contrastpre region. Further studies to investigate techniques incorporating T2-FLAIRpreregion may improve GTV delineation for salvage HFSRT.Abstract 3551; TableT1-contrastpreT2-FLAIRpreT1pre+T2preTarget overlappingDistance (cm)Target overlappingDistance (cm)Target overlappingDistance (cm)Maximum99%4.9100%4.7100%4.6Q340%2.059%2.077%2.1Median18%1.352%1.353%1.2Q112%0.824%0.826%0.7Minimum0%0.30%0.30%0.2 Open table in a new tab

Inter-observer agreement in GTV delineation of bone metastases on CT and impact of MR imaging: A multicenter study

Background and purposeThe use of Stereotactic Body Radiotherapy (SBRT) for bone metastases is increasing rapidly. Therefore, knowledge of the inter-observer differences in tumor volume delineation is essential to guarantee precise dose delivery. The aim of this study is to compare inter-observer agreement in bone metastases delineated on different imaging modalities. Material and methodsTwenty consecutive patients with bone metastases treated with SBRT were selected. All patients received CT and MR imaging in treatment position prior to SBRT. Five observers from three institutions independently delineated gross tumor volume (GTV) on CT alone, CT with co-registered MRI and MRI alone. Four contours per imaging modality per patient were available, as one set of contours was shared by 2 observers. Inter-observer agreement, expressed in generalized conformity index [CIgen], volumes of contours and contours center of mass (COM) were calculated per patient and imaging modality. ResultsMean GTV delineated on MR (45.9±52.0cm3) was significantly larger compared to CT–MR (40.2±49.4cm3) and CT (34.8±41.8cm3). A considerable variation in CIgen was found on CT (mean 0.46, range 0.15–0.75) and CT–MRI (mean 0.54, range 0.17–0.71). The highest agreement was found on MRI (mean 0.56, range 0.20–0.77). The largest variations of COM were found in anterior–posterior direction for all imaging modalities. ConclusionsLarge inter-observer variation in GTV delineation exists for CT, CT–MRI and MRI. MRI-based GTV delineation resulted in larger volumes and highest consistency between observers.

Effect of image fusion technology of radioactive particles implantation before and after the planning target and dosimetry

Objective: To compare the post-implant target volumes and dosimetric evaluation with pre-plan, the gross tumor volume(GTV) by CT image fusion-based and the manual delineation of target volume in CT guided radioactive seeds implantation. Methods: A total of 10 patients treated under CT-guidance (125)I seed implantation during March 2016 to April 2016 were analyzed in Peking University Third Hospital.All patients underwent pre-operative CT simulation, pre-operative planning, implantation seeds, CT scanning after seed implantation and dosimetric evaluation of GTV.In every patient, post-implant target volumes were delineated by both two methods, and were divided into two groups. Group 1: image fusion pre-implantation simulation and post-operative CT image, then the contours of GTV were automatically performed by brachytherapy treatment planning system; Group 2: the contouring of the GTV on post-operative CT image were performed manually by three senior radiation oncologists independently. The average of three data was sets. Statistical analyses were performed using SPSS software, version 3.2.0. The paired t-test was used to compare the target volumes and D(90) parameters in two modality. Results: In Group 1, average volume of GTV in post-operation group was 12-167(73±56) cm(3). D(90) was 101-153 (142±19)Gy. In Group 2, they were 14-186(80±58)cm(3) and 96-146(122±16) Gy respectively. In both target volumes and D(90), there was no statistical difference between pre-operation and post-operation in Group 1.The D(90) was slightly lower than that of pre-plan group, but there was no statistical difference (P=0.142); in Group 2, between pre-operation and post-operation group, there was a significant statistical difference in the GTV (P=0.002). The difference of D(90) was similarly (P<0.01). Conclusion: The method of delineation of post-implant GTV through fusion pre-implantation simulation and post-operative CT scan images, the contours of GTV are automatically performed by brachytherapy treatment planning system appears to have improved more accuracy, reproducibility and convenience than manual delineation of target volume by maximum reduce the interference from artificial factor and metal artifacts. Further work and more cases are required in the future.

Hybrid PET/MRI-based delineation of gross tumor volume in head and neck cancer and tumor parameter analysis.

Accurate target delineation allows an increase in radiation dose to the target tumor while reducing damage to the surrounding normal tissue. However, there is currently no standard for evaluating volumes measured by different imaging modalities. The aim of this study is to evaluate the feasibility of contouring gross tumor volume (GTV) by PET/MRI in head and neck cancer, and to define an adaptive threshold level (aTL) for delineating the biological target volume (BTV). Eighteen head and neck cancer patients underwent time of flight PET/MRI before chemoradiotherapy. Different GTVs of primary tumors and metastatic lymph nodes were manually contoured on MRI (GTVMRI), PET (GTVVIS), and fused PET/MRI (GTVFUS). An MRI-based GTV contour was substituted for the pathologic GTV. The percentile threshold boundary of the maximum standardized uptake value (SUVmax) for the BTV was determined when the volume of BTV approached that of GTVMRI. All GTVs were highly correlated (all Pearson's r>0.85, all P<0.001). Tumor diameter strongly correlated with GTVs (r=0.7-0.8 for all lesions and primary tumor; r=0.8-0.9 for lymph node metastases). aTL and SUVmax were moderately correlated for all lesions (r=-0.692, P<0.001) and were strongly correlated for primary tumors (r=-0.866, P<0.001). Delineating GTV on hybrid PET/MRIs is feasible, and aTL, the threshold boundary of BTV, was correlated inversely with the SUVmax.

Induction chemotherapy followed by intensity-modulated radiotherapy with reduced gross tumor volume delineation for stage T3-4 nasopharyngeal carcinoma.

PurposeA common problem in stage T3–4 nasopharyngeal carcinoma (NPC) is the narrow gap between the primary tumor and neurological structures, which makes dose optimization difficult. Considering that significant tumor shrinkage may occur during induction chemotherapy (IC), this study explored the efficacy of intensity-modulated radiotherapy (IMRT) using reduced gross tumor volume (GTV) in the treatment of T3–4 NPC.Patients and methodsBetween January 2009 and April 2014, 103 patients with non-metastatic stage T3–4 NPC were prospectively recruited. They were assigned to accept IC, followed by reduced-volume IMRT and adjuvant chemotherapy. GTV was based on the post-IC volume of intracavity tumors and lymph nodes, and the pre-IC volume of the remaining involved structures.ResultsFor all treated patients, the 3-year local failure-free survival (LFFS) was 91.9%. After IC, 91 (88.3%) patients achieved local objective response (OR), and their 3-year LFFS rates were significantly better than in patients who failed to achieve local OR (94.1% vs 75.0%, P=0.023). A multivariate analysis demonstrated the prognostic value of tumor response to IC for LFFS. Dosimetric analysis showed good homogeneity, and the dose constraints were stringent. Asymptomatic temporal lobe necrosis in the ipsilateral side of tumor occurred in one patient.ConclusionIMRT using a reduced GTV delineation delivered satisfactory doses to the target volumes and avoided overdosing of critical neurological structures. Results showed satisfactory survival outcomes with few treatment-related toxicities. Tumor response to IC could facilitate selection of patients with stage T3–4 NPC eligible for treatment with this method.

A quantitative comparison of gross tumor volumes delineated on [18F]-FDG-PET/CT scan and contrast-enhanced computed tomography scan in locally advanced head and neck carcinoma treated with Intensity Modulated Radiotherapy

&lt;p&gt;Accurate tumor diagnosis is important in highly conformal techniques such as Intensity Modulated Radiotherapy (IMRT), which aims for high therapeutic ratio. We compared Gross Tumor Volume (GTV) (primary and nodal) delineated on &lt;sup&gt;18&lt;/sup&gt;F-fluorodeoxyglucose positron emission tomography ([&lt;sup&gt;18&lt;/sup&gt;F]-FDG-PET) scan to those delineated on contrast-enhanced computed tomography (CECT) scan and its impact on staging treated by IMRT.&lt;strong&gt; &lt;/strong&gt;A total of 30 consecutive patients with locally advanced squamous cell carcinoma of head and neck were included in this study. FDG-PET and CECT scans were performed with dedicated positron emission tomography–computed tomography (PET/CT) scanner in a single session as part of radiotherapy treatment planning for IMRT. After treatment with concurrent chemoradiotherapy, all patients were followed for one year. Three out of 30 patients were excluded from the final analysis, as there was complete remission in PET/CT after neoadjuvant chemotherapy. For remaining 27 cases, the primary sites were 17 oropharynx, 2 hypopharynx, 7 larynx and 1 unknown primary with secondary neck node. PET–CT resulted in changes of CT-based staging in 25% patients (up-staged in 3 and down-staged in 4). GTV delineated on PET vs CT scan was GTV-PET (primary) of 20.15 cm&lt;sup&gt;3&lt;/sup&gt; vs GTV-CT (primary) of 18.75 cm&lt;sup&gt;3&lt;/sup&gt;, &lt;em&gt;p&lt;/em&gt; = 0.803; and GTV-PET (nodes) of 28.45 cm&lt;sup&gt;3&lt;/sup&gt; vs GTV-CT (nodes) of 21.56 cm&lt;sup&gt;3&lt;/sup&gt;, &lt;em&gt;p&lt;/em&gt; = 0.589. The mismatch between two target volumes was statistically insignificant (&lt;em&gt;p&lt;/em&gt; = 0.635 for GTV primary, &lt;em&gt;p&lt;/em&gt; = 0.187 for nodes). The mean GTV-PET outside CT for primary was 5.83 cm&lt;sup&gt;3&lt;/sup&gt;, and for node was 8.47 cm&lt;sup&gt;3&lt;/sup&gt;. Median follow-up was 12 months. One-year loco-regional control was 92%. The target delineation of GTV can be improved with functional imaging [&lt;sup&gt;18&lt;/sup&gt;F]-FDG-PET/CT.&lt;/p&gt;

EP-1333: Impact of 18 F-Choline PET scan acquisition time on delineation of GTV in Prostate cancer

Background: Dose painting radiotherapy requires accurate outlining of primary tumour volumes in the prostate. T2-Weighted (T2W) Magnetic Resonance Imaging (MRI) is the best imaging method for defining the gross tumour volume (GTV). Choline positron emission tomography (PET) is currently a controversial tracer. The image acquisition differs significantly in published studies. Many used early static imaging. One study found that 18F-choline PET/CT with late image acquisition has superior accuracy to T2W MR and functional MR alone1. We investigate whether increasing 18F-Choline PET scan acquisition time from 60 (PET-60) to 90 (PET-90) minutes improves GTV TVD. Methods. Analysis was performed on 9 18F-Choline PET scans. Patients were injected with 370MBq of activity. Three clinicians (C1, C2 and C3) independently and without reference to each other contoured GTVs on each of the T2W-MRI, PET-60 and PET-90 scans at differing times. Scans were registered by a clinician using rigid co-registration. The treating clinicians MRI contour was used as a reference contour. The resulting PET and MRI GTVs were transferred to the PET-60 and PET-90 scans after image registration. The Dice Similarity Coefficient (DSC), Specificity (Sp) and Sensitivity (S) were calculated from contour mask voxel analysis. Results. Table 1 shows the mean and range DSC, S and Sp scores on MRI, PET-60 and PET-90 for C1, C2 and C3 in comparison to the treating clinicians contour on MRI (C1). A 2 sampled T-test (P < 0.01) showed, no significant difference in the Sp, S and DSC between GTVs on PET-60 and PET-90 scans. Further to this, as shown in Figure 1, variability in GTV delineation is significant between observers in a singular case as well as across imaging modalities. Conclusion. Compared to MRI delineated GTVs, 18F-Choline PET GTVs are significantly different. This study found however that increasing the PET scan acquisition time from 60 to 90 minutes did not improve the performance of GTV TVD in comparison to MRI delineated GTV.

Volumetry of the dominant intraprostatic tumour lesion: intersequence and interobserver differences on multiparametric MRI.

Objective:To establish the interobserver reproducibility of tumour volumetry on individual multiparametric (mp) prostate MRI sequences, validate measurements with histology and determine whether functional to morphological volume ratios reflect Gleason score.Methods:41 males with prostate cancer treated with prostatectomy (Cohort 1) or radical radiotherapy (Cohort 2), who had pre-treatment mpMRI [T2 weighted (T2W) MRI, diffusion-weighted (DW)-MRI and dynamic contrast-enhanced (DCE)-MRI], were studied retrospectively. Dominant intraprostatic lesions (DIPLs) were manually delineated on each sequence and volumes were compared between observers (n = 40 analyzable) and with radical prostatectomy (n = 20). Volume ratios of DW-MRI and DCE-MRI to T2W MRI were documented and compared between Gleason grade 3 + 3, 3 + 4 and 4 + 3 or greater categories.Results:Limits of agreement of DIPL volumes between observers were: T2W MRI 0.9, −1.1 cm3, DW-MRI 1.3, −1.7 cm3 and DCE-MRI 0.74, −0.89 cm3. In Cohort 1, T2W volumes overestimated fixed specimen histological volumes (+33% Observer 1, +16% Observer 2); DW- and DCE-MRI underestimated histological volume, the latter markedly so (−32% Observer 1, −79% Observer 2). Differences between T2W, DW- and DCE-MRI volumes were significant (p < 10−8). The ratio of DW-MRI volume (73.9 ± 18.1% Observer 1, 72.5 ± 21.9% Observer 2) and DCE-MRI volume (42.6 ± 24.6% Observer 1, 34.3 ± 24.9% Observer 2) to T2W volume was significantly different (p < 10−8), but these volume ratios did not differ between the Gleason grades.Conclusion:The low variability of the DIPL volume on T2W MRI between Observers and agreement with histology indicates its suitability for delineation of gross tumour volume for radiotherapy planning. The volume of cellular tumour represented by DW-MRI is greater than the vascular (DCE) abnormality; ratios of both to T2W volume are independent of Gleason score.Advances in knowledge:(1) Manual volume measurement of tumour is reproducible within 1 cm3 between observers on all sequences, confirming suitability across observers for radiotherapy planning. (2) Volumes derived on T2W MRI most accurately represent in vivo lesion volumes. (3) The proportion of cellular (DW-MRI) or vascular (DCE-MRI) volume to morphological (T2W MRI) volume is not affected by Gleason score.

Computer-assisted framework for machine-learning–based delineation of GTV regions on datasets of planning CT and PET/CT images

We have proposed a computer-assisted framework for machine-learning–based delineation of gross tumor volumes (GTVs) following an optimum contour selection (OCS) method. The key idea of the proposed framework was to feed image features around GTV contours (determined based on the knowledge of radiation oncologists) into a machine-learning classifier during the training step, after which the classifier produces the ‘degree of GTV’ for each voxel in the testing step. Initial GTV regions were extracted using a support vector machine (SVM) that learned the image features inside and outside each tumor region (determined by radiation oncologists). The leave-one-out-by-patient test was employed for training and testing the steps of the proposed framework. The final GTV regions were determined using the OCS method that can be used to select a global optimum object contour based on multiple active delineations with a LSM around the GTV. The efficacy of the proposed framework was evaluated in 14 lung cancer cases [solid: 6, ground-glass opacity (GGO): 4, mixed GGO: 4] using the 3D Dice similarity coefficient (DSC), which denotes the degree of region similarity between the GTVs contoured by radiation oncologists and those determined using the proposed framework. The proposed framework achieved an average DSC of 0.777 for 14 cases, whereas the OCS-based framework produced an average DSC of 0.507. The average DSCs for GGO and mixed GGO were 0.763 and 0.701, respectively, obtained by the proposed framework. The proposed framework can be employed as a tool to assist radiation oncologists in delineating various GTV regions.

18-Fluorodeoxy-Glucose Positron Emission Tomography- Computed Tomography (18-FDG-PET/CT) for Gross Tumor Volume (GTV) Delineation in Gastric Cancer Radiotherapy

Purpose:Evaluation of the 18-fluorodeoxy-glucose positron emission tomography-computed tomography (18-FDG-PET/CT) for gross tumor volume (GTV) delineation in gastric cancer patients undergoing radiotherapy.Methods:In this study, 29 gastric cancer patients (17 unresectable and 7 inoperable) were initially enrolled for radical chemoradiotherapy (45Gy/25 fractions + chemotherapy based on 5 fluorouracil) or radiotherapy alone (45Gy/25 fractions) with planning based on the 18-FDG-PET/CT images. Five patients were excluded due to excess blood glucose levels (1), false-negative positron emission tomography (1) and distant metastases revealed by 18-FDG-PET/CT (3). The analysis involved measurement of metabolic tumor volumes (MTVs) performed on PET/CT workstations. Different threshold levels of the standardized uptake value (SUV) and liver uptake were set to obtain MTVs. Secondly, GTVPET values were derived manually using the positron emission tomography (PET) dataset blinded to the computed tomography (CT) data. Subsequently, GTVCT values were delineated using a radiotherapy planning system based on the CT scans blinded to the PET data. The referenced GTVCT values were correlated with the GTVPET and were compared with a conformality index (CI).Results:The mean CI was 0.52 (range, 0.12-0.85). In 13/24 patients (54%), the GTVPET was larger than GTVCT, and in the remainder, GTVPET was smaller. Moreover, the cranio-caudal diameter of GTVPET in 16 cases (64%) was larger than that of GTVCT, smaller in 7 cases (29%), and unchanged in one case. Manual PET delineation (GTVPET) achieved the best correlation with GTVCT (Pearson correlation = 0.76, p <0.0001). Among the analyzed MTVs, a statistically significant correlation with GTVCT was revealed for MTV10%SUVmax (r = 0.63; p = 0.0014), MTVliv (r = 0.60; p = 0.0021), MTVSUV2.5 (r = 0.54; p = 0.0063); MTV20%SUVmax (r = 0.44; p = 0.0344); MTV30%SUVmax (r = 0.44; p = 0.0373).Conclusion:18-FDG-PET/CT in gastric cancer radiotherapy planning may affect the GTV delineation.